the motor is a 351w fresh built, 600cfm edelbrock carb, and edelbrock proformer intake, headers. im gonna put some short gl*** packs in-line, running duals all the way back. so for performance and motor health wise, any thoughts on what size exhaust pipe i should run?
I would go with 2.5. No bigger then 2.75. I have a 450hp 383 and im running 2.5 exhaust. I would like to step up to 3" eventually though just because i have gobbs of torque and wouldnt hurt me to lose a few. This same engine was set up with 3" and it seemed to run better. 3" is alittle louder too.
Oh yea. You didnt mention anything extreme about your engine. Meaning its a pretty mild manored setup thats how i came up with the 2.5 inch exhaust.
Smaller diameter pipe helps keep up exhaust velocity = more torque...larger diameter pipe = more HP...generally speaking...
I'm ***uming stock iron heads, since you didn't mention them. 2 1/4 should be fine. If they are ported on the ex side, or are aftermarket, I'd go 2 1/2.
2.25 (mandrel bends) is big enough for any street small block.The bigger you go, the tighter it will be through the frame,over rearend,etc. Anything bigger than 2 1/4 would be overkill.
i'd go 2" with an H somewhere between the collectors & the gl*** packs. it will sound sweet with good torque without to much back pressure.
wow, thanks for the feedback! what exactly is a mandrel bend? just a smooth bend as opposed to the crinkled inside bends? (which I'm ***uming have a name too)?
I put 2.5" on my 39 with a 408, it is too damn big, if I had it to do over I would go with nothing bigger than 2". IMO the 2.5" pipes are a WASTE and they take up too much room. Besides, I think smaller pipes sound better.
ok so 2'' sounds like the majority vote. thanks!! now for futures sake, this is for a 47 ford pickup, and say i wanted to have 2 stacks through the bed hugging the cab, would this change what size i should use?
2 1/4 is great for what you have, an H-pipe is great but an X pipe is better but you might not have the room to do it and it would not be a huge performance gain over an H-pipe. I have to agree with everybody on here about 2 1/2 pipe is just not worth it. Jon
2 1/4" Mandrel bend to rear bumper with least amount of bends. Small block Olds ported and polished with lumpy cam and a few other flow balance tricks. Single 4 bbl. Q-jet through non chambered gl*** packs. Still quiet when needed, rips the air when you want to. Balance seems to be just right. Glad I didn't go any bigger.............
A mandrel bend is not smashed on the inside of the bend like a muffler shop bend.As the tubing bends,a mandrel (series of rollers) that kind of looks like a caterpillar is pulled through the tubing.It leaves the bend the same diameter as the straight tubing.It is more expensive,but worth it for sound quality alone even if you're not concerned with performance. Also, I always put the mufflers as far back as possible,sounds better.A long,small diameter tailpipe with few bends will cause that tacky "hillbilly cackle" which just sounds like hell.
Love the 2.5" full mandrel bent with Flow 40's dumped right before the axle on my mild 289. I may be giving up a little torque, but it has plenty. 3" is WAY to big....anything from 2" to 2.5" should fit your bill.
Anything more than 2" is a waste of your torque curve and pulling power. The stacks will make little difference in the size of pipe required to maintain your torque curve. ..... you either go up (5 or 6 feet) at the back of the cab or you go back another 6 feet from the back of the cab, it's all just a tailpipe as far as the engine is concerned. jmho moe .
If your exhaust is going to be visible then definitely no bigger than 2 inches - anything bigger will look too modern. And I'll second that smaller pipes sound better most of the time. I had a 302 in a '50 Ford with 1 3/4" pipes and gl*** packs and that bone-stock motor sounded fantastic.
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